The present invention relates to a cleaning and disinfecting method for a contact lens, and more particularly to a cleaning and disinfecting method for a contact lens, which detoxicates a hypohalogenous acid in a short period of time after showing excellent cleaning and disinfecting effects of the hypohalogenous acid.
A contact lens has some apprehensions that eyes are injured when the contact lens is continuously worn in eyes as it is for a long period of time because stains in the surroundings, microbes, proteins contained in tear fluid, and the like adhere to the contact lens while the contact lens is worn in eyes. Accordingly, there is a necessity to clean up or disinfect the contact lens regularly, preferably every day.
As a cleaning method for a contact lens, a method comprising washing the contact lens with a solution containing a surface active agent by fingers has been conventionally known, and according to this method, stains on the surface of the contact lens can be removed. However, for instance, when the method is applied to a hard contact lens, there is an apprehension that the hard contact lens is broken or damaged during washing. Also, when the method is applied to a water-absorptive soft contact lens, stains such as proteins, which are incorporated in the contact lens, cannot be completely removed.
Also, as a cleaning method for regenerating and reusing a contact lens stained with proteins, a method comprising using a cleaning agent containing a proteolytic enzyme has been conventionally known. When this cleaning method is used, although proteins adhered to the surface of the contact lens can be decomposed, it takes a long period of time to decompose proteins because the enzyme is used. Especially, when a water-absorptive soft contact lens is cleaned up by using the cleaning agent, besides taking a longer period of time for treating the water-absorptive soft contact lens in comparison with the period of time for treating a hard contact lens, sufficient removing effects of proteins cannot be expected because the proteolytic enzyme itself should be incorporated in a contact lens so that proteins being denatured in the internal of the contact lens can be decomposed.
U.S. Pat. No. 4,732,185 discloses a cleaning method for a contact lens comprising establishing an electric field in a determined direction in a boric acid-EDTA buffer solution having pH 8 to 9 and immersing a contact lens in the solution to remove proteins from the contact lens by electrophoresis. When this method is carried out, proteins incorporated in a water-absorptive contact lens can be surely removed. However, the method requires that proteins should not be denatured and are ionized, and there are some problems in the method such that it takes a long period of time for the treatment.
On the other hand, as a disinfecting method for a water-absorptive contact lens, there have been known a method comprising immersing a contact lens in aqueous hydrogen peroxide to disinfect the contact lens and decomposing hydrogen peroxide with a metallic catalyst, a reducing agent and an enzyme catalyst to detoxicate the solution, a disinfecting method comprising making use of a compound such as chlorhexidine, and the like.
However, according to the above-mentioned method of using aqueous hydrogen peroxide, besides taking a long period of time for the treatment since hydrogen peroxide remaining in the water-absorptive soft contact lens should be decomposed, stimulation such as smarting of eyes occurs if hydrogen peroxide remaining in the internal of the water-absorptive contact lens is not completely decomposed. Therefore, the above method is not a suitable method for disinfecting a water-absorptive contact lens. Also, according to the above-mentioned disinfecting method of using a compound such as chlorhexidine, there is a danger such that the compound is adsorbed to the lens or allergosis against eyes occurs by the remaining compound.
On the other hand, by using a disinfecting method comprising using hypochlorous acid, pathogen in eyes such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa or Candida albicans can be disinfected with hypochlorous acid in a concentration of several ppm in a short period of time, and stains of organic substances such as proteins adhered to the lens can be removed.
As a method comprising using hypochlorous acid, Japanese Unexamined Patent Publication No. 68454/1981 discloses a method comprising generating hypochlorous acid by electrolysis to disinfect a contact lens. However, according to this method, a contact lens should be immersed in a hypochlorous acid solution for a long period of time since it takes a long period of time to naturally dissipate hypochlorous acid remaining after the treatment. Therefore, when the method is used, there are problems such that color of the contact lens is decolored and that a mark printed on the contact lens is discolored.
A method comprising inactivating hypochlorous acid remained after a disinfecting treatment by using a suitable metallic catalyst or a suitable reducing agent has been proposed because a lens disinfected by using hypochlorous acid cannot be worn in eyes as it is. As the above-mentioned method, for instance, there have been known a method comprising reducing and detoxicating hypochlorous acid with a metallic catalyst as described in Japanese Unexamined Patent Publication No. 19218/1993, a method comprising reducing and detoxicating hypochlorous acid with a reducing agent as described in Japanese Unexamined Patent Publication No. 106492/1975 and Japanese Unexamined Patent Publication No. 1.90214/1992, and the like.
Several problems occur when hypochlorous acid is reduced after a disinfecting treatment using the method described above. The reduction procedures themselves are complicated, and aspectic conditions are difficult to maintain. Also, when the reduction procedures are not carried out exactly as instructed, the disinfected contact lenses may cause injury to the eyes of the wearer. And since the lenses are exposed to a high concentration of hypochlorous for an extended period of time while the hypochlorous acid is being reduced, deterioration of the lens or the fading of a colored lens may occur.
Japanese Unexamined Patent Publication No. 2544 16/1988 and Japanese Unexamined Patent Publication No. 254417/1988 propose a method comprising separating an electrolyte solution in a cleaning bath into two rooms by a diaphragm to which an ion-exchange membrane is applied, applying a direct current to the electrolyte solution to generate an acid solution containing hypochlorous acid and an alkali solution, cleaning a contact lens in the alkali solution and applying an electric current in reverse to the electrolyte solution to neutralize the alkali solution in which the contact lens is immersed. However, according to the method, although pH of the alkali solution in which the contact lens is immersed becomes neutral, the generated hypochlorous acid is not reduced and remains in the solution, so that there is a problem that the contact lens cannot be worn in eyes as it is after the treatment.
The present invention has been accomplished in consideration of the above prior art.
An object of the present invention is to provide a cleaning and disinfecting method for a contact lens, which cleans up and disinfects a contact lens with excellent disinfecting activities and excellent cleaning activities of a hypohalogenous acid, and detoxicates the hypohalogenous acid in a short period of time.
Another object of the present invention is to provide an electrical treating method for a contact lens, which heightens electrical safety against an electric shock and an electric leakage by lowering electric power as much as possible, and can be preferably used for a treating apparatus for a contact lens which is convenient for carrying by using an electric cell, a battery, and the like.
These and other objects of the present invention will become apparent from the description hereinafter.